The cystic fibrosis data base has collected extensive data on patients coming to clinic for treatment. The purpose of this project is to characterize the longitudinal course of pulmonary function in these patients, including profiling of the infection history of individuals. In these analyses, methods for summarizing the clinical course for individual patients are being developed. Relationships between clinical course and infection history to factors such as gender, the nature of the cystic fibrosis mutation (genotype), and age will be examined. Predictive models of change in pulmonary function based upon such factors as well as prior course will also be considered.